Advancement in technologies has led to demand for high-data processing performance of semiconductor devices, and hence a great deal of research has been directed to development of high-speed semiconductors to cope with such a trend. High-integration of semiconductors is necessary to satisfy high-speed requirements in semiconductors, and consequently the planarization of semiconductor wafer has become an essential factor for the realization of semiconductor integration to a desired level. Such requirements for the realization of high-speed semiconductors have led to incorporation of the polishing process into the semiconductor manufacturing processes. The polishing pad is a consumable pad that is used in the planarization process of materials requiring a high degree of surface flatness as described above, and is therefore widely used in planarization of various materials requiring a high degree of surface flatness, such as glass, mirror and dielectric/metal composite, as well as semi-conductor integrated circuits.
Polishing generally consists of the controlled wear of an initially rough surface to produce a smooth specular finished surface. This is commonly accomplished by rubbing a pad against the surface of the article to be polished (the workpiece) in a repetitive, regular motion while a solution containing a suspension of fine particles (the slurry) is present at the interface between the polishing pad and the workpiece.
Examples of conventional polishing pads may include felted or woven natural fibers such as wool, urethane-impregnated felted polyester or urethane pads filled with various kinds of fillers, or urethane pads containing no filler but having micro-holes or gas bubbles or pores capable of storing the polishing slurry.
As prior arts relating to the polishing pads, mention may be made of a polishing pad utilizing protruded fibers in conjunction with voids, via incorporation of urethane into polyester felt (U.S. Pat. No. 4,927,432), IC-series, MH-series and LP-series polishing pads having a surface structure made up of semicircular depressions by incorporation of hollow spherical elements or pores and gas bubbles into polyurethane (manufactured by Rohm and Haas), a polishing pad having a characteristic surface structure made up of protrusions and concavities with or without use of filler particles (U.S. Pat. No. 5,209,760), a polishing pad comprising high-pressure gas-containing hollow fine spheres or water-soluble polymer powder dispersed in a matrix resin such as polyurethane: (Japanese Patent No. 3013105 and Japanese Patent Publication Laid-open No. 2000-71168). Therefore, techniques applied to the polishing pads as described above are primarily based on incorporation of different kinds of materials (such as pores, gas bubbles, fillers, felt and non-woven fabric) into the polyurethane matrix via a variety of methods.
The polishing pad utilizing protruded fibers together with voids via incorporation of urethane into polyester felt, as disclosed in U.S. Pat. No. 4,927,432, exhibits superior planarity, but disadvantageously suffers from a slow polishing rate due to low hardness of the pad itself. IC-series, MH-series and LP-series polishing pads having a surface structure made up of semicircular depressions by incorporation of hollow spherical elements or pores and gas bubbles into polyurethane, commercially available from Rohm and Haas, are currently widely used due to superior polishing rate and planarity, but incorporation of heterogeneous hollow spherical elements or pores/gas bubbles dis-advantageously results in the difficulty of uniform dispersion, thereby leading to a difference in density between the polyurethane matrix and incorporated materials, and the flatness error is gradually increased as the polishing progresses. The polishing pad having a characteristic surface structure consisting of protrusions and concavities with/without use of filler particles, as disclosed in U.S. Pat. No. 5,209,760, also suffers from difficulty in uniform dispersion of heterogeneous filler particles. Further, the polishing pad comprising high-pressure gas-containing hollow fine spheres or water soluble polymer powder dispersed in a matrix resin such as polyurethane, as disclosed in Japanese Patent No. 3013105 and Japanese Patent Publication Laid-open No. 2000-71168, disadvantageously suffers from difficulty of dispersion associated with mixing of the water-soluble polymer powder, and decreased hardness of the pad surface as the polishing process progresses, thus resulting in changes in the polishing rate.
In addition, a polishing pad in a uniform urethane non-foam system (for example, IC-2000 manufactured by Rodel) may be mentioned wherein polishing performance is imparted to the pad using surface texture. However, such a polishing pad suffers from a problem of scratches occurring on the polished surface of a workpiece, and therefore is not widely used at present. Further, the polishing pad in the non-foam system cannot maintain sufficient amounts of the polishing slurry on the surface of the pad at the time of polishing, and is thus not preferable from the viewpoint of polishing rate.
That is, as a principal polymer matrix obtained by blending, mixing, solidification and impregnation of pores, gas bubbles, fillers and non-woven fabric, a pad having desired elasticity and hardness and using a polyurethane matrix taking into consideration manufacturability has been primarily used as the polishing pad. To this end, pads, which include the above-mentioned heterogeneous materials, pores or gas bubbles, or heterogeneous materials capable of forming concavities during the chemical-mechanical polishing (commonly abbreviated as CMP) process in the polyurethane matrix, are commercially available and are widely used in planarization processes of various semiconductor materials or planarization processes of glass surface.
However, inclusion of pores or gas bubbles in the polyurethane matrix disadvantageously leads to an increase in density difference due to non-uniformity of dispersion, which consequently brings some differences in the polishing performance from lot to lot and also density variation within the corresponding lots from part to part, and an increase in the flatness error as the polishing operation progresses. Pads containing water-soluble fillers in the polyurethane matrix are known to form pores and concavities by polishing slurry, thus improving the polishing performance via the use of the-thus formed pores and concavities. However, these pads have shortcomings in that hardness of the pad is decreased with a further progress of the polishing operation, thereby decreasing the polishing rate, and wearing of the pad leads to the shortened service life of the pad.
In addition, there may be mentioned a polishing pad containing laser-formed micro holes in a uniform urethane matrix which is commercially available from the present applicant.